hmm, i'm pretty sure rune devoured a symbiote in the xover he and venom had, but i seem to recall venom having an upperhand in the fight. i'd need to look back over the issue, but if he DID devour the symbiote, i'd likely have to go with rune.
rune was a tricky bugger to figure. he battled everyone from conan to thor to warlock (whom i belive he defeated at least once and forced into a healing cocoon) to the surfer . . . 😬